Such investigations may be performed in the open air or in an anechoic chamber (anechoic for microwaves). The invention is particularly suitable for the second case.
The fixed microwave emitter/receiver which is pointed towards the mock-up must be capable of accurately measuring its backscattering characteristics. In theory, the position at which the mock-up is located is fixed, however it is necessary to provide for varying the height of the mock-up relative to the microwave illumination axis. Further, depending on its scale, the mass of the mock-up may be as much as several hundred kilograms.
One difficulty then lies in the need for the support (or positioner) itself to backscatter microwaves very little, in other words, its radar echo area or cross-section must be small.
It is also necessary for the attitude and the position in three dimensions of the mock-up to be accurately known for each of the microwave measurements. In the present specification, a "microwave measurement" is constituted by a full set of information that can be acquired by the emitter/receiver. Its duration is related, for example, to the form factor which is the product of pulse duration multiplied by recurrence frequency when considering a Doppler pulse radar. Similarly, "attitude" is taken in its widest sense (roll, pitch, relative bearing).
Up to now, mock-up supports such as a pole or a block of foam have been used in association with suitable positioning means.
Further, the position and the attitude of the mock-up have previously been determined by mechanically or optically tracking the attitude of the supports.
It is now becoming desirable to work with mock-ups that backscatter little or very little, and as a result these known devices are becoming unsuitable.
The object of the present invention is to provide mock-up positioning means which, themselves, have a very small radar echo area (REA).
Another object of the invention is for said REA to remain very small regardless of the attitude of the mock-up, which attitude may be modified continuously, particularly in relative bearing.
Another object of the invention is to make it possible to accurately measure the attitude of the mock-up, in particular relative bearing rotation, without requiring marker devices to be applied thereon, since such market devices could alter the backscattering from a very low REA mock-up, and without requiring devices for tracking the attitude of the supports.
Another object of the invention is to ensure that the attitude of the mock-up remains stable while microwave measurements, as defined above, are being performed.